Where do glaciers occur in the Sierra Nevada?

The number of glaciers in the Sierra Nevada depends on the definition. The definition of a glacier is a body of perennial ice or snow that moves. Movement of ice can be observed as cracks in the ice known as crevasses. Because Sierra Nevada glaciers are small and remote previous glacier inventories have placed the number between 50 and 500 glaciers. My survey, based on USGS topographic maps (1:24,000 scale), counted over 1700 glaciers and snow and ice patches. Many snow and ice bodies which do meet the definition of a glacier. I estimated the number of "true glaciers" at 118 glaciers in the Sierra Nevada based on theoretical considerations.

Sierra Nevada glaciers have become smaller over the past century. This is evident from early photographs which reveal these glaciers occupying their moraines around 1900. Today, the glaciers have receded up the mountains and appear deflated. I quantified the surface area change by selecting fourteen glaciers throughout the Sierra Nevada and measured the change using historical photographs, geologic evidence, and field mapping. I determined the glaciers lost and average of 55 percent of their surface area by 2004. The decrease in surface area of individual glaciers ranged between 31 and 78 percent.

Glacier Repeat Photography 

Comparisons of the repeat photographs reveal that all ten glaciers surveyed in 2003 and 2004 have experienced a reduction in ice volume and surface extent over the past century. Repeat photography is a valuable tool in determining change through time, especially when combined with aerial photos and field measurements.
Please contact me if you are interested in using these photographs.